神经经济学研究

Cite:

Zak, P. J. . "Neuroeconomics." Philosophical Transactions of the Royal Society B Biological Sciences 359.1451(2004):1737.

Introduction:

Ø Economics: the optimal allocation of scarce resources. Models the individuals valuing rewards and choosing among alternatives.

· Obtaining information from the environment regarding possible actions

· Valuing those actions

· Choosing between them

Ø Bioeconomics: uses evolutionary biology to build models that predict human behavior

Ø Behavioral economics: uses findings from cognitive psychology to better model human decision-making

Ø Economics of choice:

· Solitary choice: are made with little or no input from others and are non-strategic.

o 比如说从两个offer里选要去哪一个，utility function

o Finding an equilibrium produces maximal utility subject to constraints

o Predicts behavior in impersonal exchange (in markets)

· Strategic choice: game theory

Basic Brain Facts and Terminology

Ø Two sides to the autonomic nervous system: controlled by hypothalamus （下丘脑）

· Sympathetic responses:

o 4 Fs (fright, flight, fight and foinication)

o arousing

· Parasympathetic（副交感的） nervous system:

o activate when it is time to rest and digest

o relaxing

Ø Emotional responses:

· Limbic structure: includes amygdala（扁桃腺）: positive and negative emotions

· Hippocampus（海马）: long-term memory

· Cingulate cortex: attention and error detection

· Olfactory cortex: smell

Ø Measurement of brain activity

· PET:

o Injects radio-active isotopes that emits positrons, positrons and electrons annihilate and emit gamma ray

o measures the accumulation of the radioactive tracer in brain regions; regions metabolizing glucose faster receive more blood flow and emit more gamma rays

· fMRI:

o natural firing increases the demand for oxygenated blood. Examining oxygenated and deoxygenated blood

o deoxyhaemoglobin is paramagnetic, it produces a measurably larger signal relative to oxyhaemoglobin

o limitations: external confound must be eliminated（因为很敏感）

o 几乎没有副作用

· Hyperscanning

o Tow or more subjects in MRI scanner in different locations and working through internet

o One brain affects another brain

· EEGs/ERPs

o Measure the electrical activity of large groups of neurons

o Tracing waves

o Higher temporal resolution but lower spatial resolution, electrodes placement depending on bony landmark（位置可能会不精确）

Major Finding in Neuroeconomics

Ø Research topics categories:

· Identifying the neural processes involved in decisions in which standard economic models predict behavior well

o Headed by neuroscientist or M.D

· Studies of “anomalies” where the standard models fail

o Led by economists

Ø Reward acquisition:

· 62.5% of area LIP neuron activation was correlated with expected gain （动物实验，奖赏、惩罚）

· The utility function that economists presumed existed to explain behavioral data is a physiological reality in area LIP: area LIP neurons perform the calculations needed to determine utility

o LIP firing rates can be used to predict the behavior of monkeys in several reward acquisition tasks

· Motivation mechanisms:

o dopaminergic neurons process rewarding stimuli, firing proportional to the error of the actual to the expected reward

· Gains produced neural rewards, whereas losses provoked emotional responses associated with fear or regret

o 通过一些列实验进一步细化这个reward的过程和区域

o Subjective states associated with utility must have an emotional basis –utility must be felt to be valuable: MPFC and the OFS circuit appear to map “wanting” to “having”

o Risk aversion over gains but not losses

o Varying the stimulus and/or measurement modality can produce different regional activation maps. Interpretive caution is called for.

Ø Certainty, ambiguity and gratification delay

· Emotions are important for choice

o 大脑感知emotion区域damage的病人无法做决定

o Amygdala activation was predictive of an anticipated loss

o Emotional activation during decisions may be more likely to occur with incomplete information, risk, or choice in a social context.

o The suppression of limbic responses may be part of what makes human choice different from choice by animals.

· Subjects showed strong ambiguity aversion, but ambiguous and partly ambiguous choices did not generate activation in brain regions associated with emotions

· Choosing between immediate and delayed gratification constitutes a battle between limbic structures that activate for current reward and newer cortical regions that evaluate trade-offs.

Ø Learning and strategy

· 猴子在玩matching penny的时候会update and learning, using experience

Ø Cooperation

· Hypothesized that cooperative behavior would require that subjects use a brain region associated with “theory of mind” in which a person is able to anticipate what another will do by imagining himself/herself in the same situation

· Trust games:

o BA10 allows gratification delay in order to obtain larger rewards through cooperation

· Cooperation is rewarding, requires attention and the mediation of the conflicting concerns of making more money but behaving in socially less acceptable ways, and has an emotional component.

· Somatic marking theory

o Linking emotions “experienced” in the body with decisions

o Somatosensory association cortex activates during memory, attention and emotional responses to objects

· Low offers in the ultimatum game are rejected because of a sense of disgust

· Neuro active hormone OT would process signals of trust and induce trustworthy behavior

o DM2s receiving trust signals had OT levels almost twice that of DM2s in a control task

o Higher OT levels in DM2s were strongly associated with trustworthy behavior

o Women who were ovulating were less trust worthy than other subjects (progesterone变多，progesterone is known to inhibit OT uptake

o OT is released in response to a signal of trust, rather than being a primary trait of subjects

o OT is a positive motivator of cooperation

The Future: Convergent Evidence

Ø Convergent evidence: using different measurement modalities, subject groups, and moving from correlations to causation

Ø 例1：孤独症患者在做游戏的时候并没有表现出不会合作的问题，但在重复博弈时却无法习得任何策略。Because autistics have not developed social “fairness” rules that most healthy individuals have internalized through repeated social interactions.

Ø 例2：adolescents had lower average BOLD signal than young adults for the same sized rewards. Indicates that one reason adolescents may engage in risky behaviors is to compensate for hyperactive reward activity in their brains.

Neuroeconomics and the Law

Ø Neuroeconomics experiments varies the “laws” and allow subjects to make choices under legal regimes could be an important step towards better public policy.

· How much of it can be traced to nature and nurture?

· Laws designed to prohibit personal moral violations must activate brain regions associated with understanding others to be effective

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